Optically readable tags encode data in an optically readable format. Some optically readable tags, such as bar codes, are considered to be one-dimensional in that the tags encode information in a format that can be read via a scan along one direction. Other tags are considered to be two-dimensional in that the tags encode information along two directions. Two dimensional tags may be read by an optical imaging device, such as a charge-coupled device or CMOS imaging device.
An amount of information encoded by a tag may be increased per unit area by increasing a density of the features on the tag that are used to represent bits of data. For example, in a two-dimensional tag that encodes data in the form of small rectangular features, the bit depth of the tag may be increased by increasing a number of the rectangular features per unit area. However, the resulting decrease in size of the data features on a tag may increase the difficulty of reading a tag, as the data features may appear blurred to an imaging device used to read the tag if the tag is in motion during reading.